Titanium phosphate superflint glass



Jan. 20, 1970 G. F. BREWSTER ET TITANIUM PHOSPHATE SUPERFLINT GLASS 2 Sheets-Sheet 1 Filed Jan. 23, 1967 Om mm @W m? Om mm Ow mhzjm All, mz omo III-V,

u )xaom smmvasaa GORDON F BREWSTER ROBERT A. WEIDEL INVENTORS ATTORNEY Jan. 20, 1970 G. F; BREWSTER ET AL 3,490,923

TITANIUM PHOSPHATE SUPERFLINT GLASS 2 Sheets-Sheet 2 Filed Jan. 23, 1967 FIG. 2

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WAVELENGTH (MILLIMICRONS) GORDON F. BREWSTER ROBERT A. WEIDEL INVENTOR3 BY 4f 7M4 ATTORNEY United States Patent 3,490,928 TITANIUM PHOSPHATE SUPERFLINT GLASS Gordon F. Brewster, Williamson, and Robert A. Weidel,

Webster, N.Y., assignors to Bausch & Lomb Incorporated, Rochester, N.Y., a corporation of New York Filed Jan. 23, 1967, Ser. No. 610,971 lint. Cl. (303s 3/16, 3/30; G02b 1/00 U.S. Cl. 10647 9 Claims ABSTRACT OF THE DISCLOSURE DESCRIPTION This invention relates to phosphate glasses containing titanium dioxide. Prior glasses containing large amounts of titanium compounds have been characterized by a deep purple color which rendered them unsuitable for many optical uses. It has been discovered that this undesirable property is eliminated by introducing arsenous oxide into the glass batch. The resulting glasses have an acceptable yellow color similar to that of high flint glass and the glass materials can be used in various optical instruments, such as microscopes.

The glass former is, P 0 introduced as metaphosphate. Aluminum metaphosphate is desirable since it is the most chemically durable of the rnetaphosphates, at the same time having a high melting range. Alkali metal metaphosphate is added to lower the melting temperatures of the system and, the alkaline earths are used to adjust other physical and optical properties. Where high amounts of titanium oxide are added to the batch, it has been found necessary to add boric oxide in order to retain the TiO in the glass matrix.

In making up the glass batch, it is preferred to add the aluminum, alkaline earth and alkali metal oxides in the form of metaphosphate salts, e.g., A1(PO Mg(PO and KPO because this method for introducing the components results in minimum loss of P 0 by volatilization during the melting step. The total amount of the metaphosphates is generally less than 80 weight percent in the batch composition.

Orthophosphates, such as BPO may be added to some of the compositions, but these additives require higher melting temperatures, resulting in excessive AS203 losses. Also, substantial devitrification of the glass occurs when more than about 3 Weight percent of boron orthophosphate is used. Up to 20 weight percent lead metaphosphate is acceptable to achieve certain indices.

3,490,928 Patented Jan. 20, 1970 Magnesium metaphosphate is the preferred alkaline earth compound, and may be used from about 5 to 40 Wt. percent. Calcium and barium oxides may be introduced without detrimental effects up to about 10 weight percent (based on the metaphosphate).

Potassium metaphosphate can be used in wide proportions (about 5 to 35 wt. percent). Other alkali metal compounds containing sodium or lithium may be used in part. For example, up to 20 weight percent LiPO may be added to adjust the refractive index and Abbe value of a particular glass.

Aluminum metaphosphate (about 5 to 40 wt. percent) is important to achieve the optimum quality product having high durability and low devitrification properties, when combined with the other constituents. Fairly large amounts of TiO can be introduced into the glass matrix in the absence of B 0 however, the introduction of boric oxide allows larger amounts of TiO to be added and stabilizes (for devitrification) other compositions. Boric oxide is usually added as B(OH) in an amount sufiicient to give a TiO :B O weight ratio of about 1:1 to 9:1.

Suflicient arsenous oxide is added to the batch to substantially decrease the purple color ordinarily present when titanium oxide is present in the glass. The TiO t- AS203 weight ratio of about 0.8:1 to 10:1 has been satisfactory for eliminating the purple color.

Accordingly, it is an object of this invention to provide new glass compositions having valuable optical properties. Another object is to decrease the purple color of titanium oxide glasses by addition of arsenous oxide to the glass batch. Yet another object is to provide a batch composition of metaphosphate compounds of aluminum, alkali metals and alkaline earth metals containing sufficient boric oxide to permit large amounts of titanium oxide to be retained in the glass, and sufficient arsenous oxide to decrease the color attributed to the presence of titanium oxide. A further object is to provide a high-titania glass useful for optical instruments. These and other objects and features of the invention will be seen in the following description of examples and in the drawing, wherein:

FIG. 1 is a graphic plot of the refractive index and Abbe value for several titanium phosphate superfiint glasses, comparing these properties with known optical materials; and

FIG. 2 is a graphic plot 'of radiation transmittance showing its change with Wavelength in the visible region of the electromagnetic spectrum.

The results of numerous glass melts have been tabulated to show the effect of titania and arsenous oxide on the optical properties of the glass. In Table I, the refractive index is shown for the sodium D line (589.29 millimicrons) and the reciprocal dispersion is expressed as the Abbe value (1/=n ln n where it and n are the refractive indices for 486.13 and 656.29 millimicrons, respectively).

TABLE I Batch Constituents, Weight Percent Optical Properties Refractive Abbe index Values Example NO. A1(PO3)3 Mg(PO )2 KPO3 B203 T102 AS20 (71 (11) 36. 5 12. 7 17. 8 7. 5 22. 2 3. 3 1. 6698 27. 2 36. 2 12. 6 17. 6 6. 2 22. 5. 1. 6739 26. 6 34. 7 11. 7 16. 3 4. 9 27. 0 5. 4 1. 7090 24. 2 32. 5 11. 2 15. 7 4. 9 32. 5 3. 2 1. 7410 22. 8 32. 2 11. 1 15. 5 3. 6 32. 2 5. 4 1. 7475 22. 4 0. 0 27. 8 20. 6 6. 2 22.0 5. 5 l. 6768 27. 2 18. 0 l2. 6 35. 8 6. 2 22. 0 5. 5 1. 6753 26. 8 20. 0 32. 8 19. 6 6. 2 16. 0 5. 5 1. 6367 30. 8 21. 0 33. 8 20. 6 0. 2 13.0 5. 5 1. 6138 33. 5 22. 0 34. 8 21. 6 6. 2 10. 0 5. 5 1. 5890 37. 4 23. 0 35. 8 22. 6 6. 2 7. 0 5. 5 l. 5682 42. 2 17. 0 29. 8 16. 6 9. 2 22. 0 5. 5 l. 6748 27. 6 16. 0 28. 8 15. 6 l2. 2 22. O 5. 5 1. 6767 27. 9 15. 0 27. 8 14. 6 15. 2 22. 0 5. 5 1. 6727 28. 3 16. 0 28. 8 l5. 6 6. 2 22. 0 11. 5 l. 6955 26. 4 15. 0 27. 8 14. 6 6. 2 22. 0 14. 5 l. 7015 26. 0 14. 0 26. 8 13. 6 6. 2 22. 0 17. 5 l. 7104 25. 6 13. 0 25. 8 12. 6 6. 2 22. 0 20. 5 1. 7191 25. 1 12. 0 24. 8 11. 6 6. 2 22. 0 23. 5 1. 7261 24. 8 l1. 0 23. 8 10. 6 6. 2 22. 0 26. 5 1. 7049 25. 4 18. 0 30. 8 l7. 6 6. 2 22. 0 5. 5 1. 6886 27. 0 l9. 0 31. 8 18. 6 6. 2 19. 0 5. 5 1. 6639 28. 5 l8. 0 30. 8 17. 6 7. 2 20. 0 6. 6 1 6718 28. 6

The titanium phosphate superfiints shown in Example Nos. 1 to 23 of Table I, have been plotted with respect to their optical properties in FIG. 1. These glasses display an Abbe value (11) lower than other flint glasses for a given refractive index, and this property is extremely valuable in providing design flexibility for the optical designer.

The relative proportions of the batch constituents can be varied widely to produce the desired glass product. The limits of oxide percentages in the glass are shown in Table II for the individual compounds. This tabulation shows the broad, preferred and optimum percentages of each oxide, independently of the particular combination of oxides (e.g., metaphosphates) which make up the batch.

TABLE II Weight Range (percent) Glass Component Broad Preferred Optimum The glass of Example 22 is typical of the titanium phosphate superflints in its heating schedule to convert the batch constituents to a glassy reaction product. For a ten-pound melt, the mixed batch particles are filled over a period of three hours into a platinum melting pot at 1200 C. The melt is fined and stirred for about 19 hours at 1230 C., and cooled in 1.5 hours to 1150 C. At this temperature, the molten material is cast on a mold preheated to 300400 C. Then the cast glass is annealed for about 12 to 20 hours at 550 C. Variations in the schedule for a particular melt size or composition will be readily determined by a skilled glassmaker. When large amounts of arsenous oxide are included in the melt, some loss due to volatility can be expected. However, this can be minimized by using relatively low melting temperatures.

The titanium phosphate superflint of Example 22 is a preferred embodiment of the invention, and carires an I.C.T. designation of Type 664/285. Its yellow color is comparable to very high flint glasses. As shown in FIG. 2, the transmittance decreases with shorter wavelength toward the ultraviolet region of the electromagnetic spectrum, typical of flints. Above about 500 millimicrons, the transmittance is nearly constant.

Table III shows the results of highly-accurate refractive index measurements for the Type 664/ 285 glass of Example 22. I

TABLE III Wavelength (millimicrons) Refractive index The cold working properties of the titanium phophate superflints are normal, and the glass reacts well to grinding, polishing, sawing and other similar operations.

Various glass modifiers may be added to the new glasses within the skill of the glas smaking art without departing from the inventive concept.

What is claimed is:

1. A glass composition consisting essentially of TiO P 0 A1 0 alkaline earth oxide, alkali metal oxide, B 0 and AS203, the glass having a refractive index (n of about 1.6 to 1.75 and Abbe value (11) less than about 40 wherein the glass batch constituents are present in the following weight percent ranges:

A1 0 1 to 10;

alkaline earth oxide, 1 to 10;

alkali metal oxide, 1 to 20;

TiO 7 to 35; and

AS203, 3 to 30.

2. A glass composition consisting essentially of TiO P 0 A1 0 alkaline earth oxide, alkali metal oxide, B 0 and AS203, the glass having a refractive index (n of about 1.6 to 1.75 and Abbe value (11) less than about 40 wherein the glass batch constituents are present in the following weight percent ranges:

alkaline earth oxide, 2 to 8;

alkali metal oxide, 4 to 15;

P 0 40 to 55;

B 0 4 to 15;

TiO 8.5 to 25; and

A5203, 4 to 7- 3. A glass composition consisting essentially of TiO P A1 0 alkaline earth oxide, alkali metal oxide, B 0 and AS203, the glass having a refractive index (n of about 1.6 to 1.75 and Abbe value (11) less than about 40 wherein the glass batch constituents are present in the following weight percent ranges:

alkaline earth oxide, 5 to 7;

alkali metal oxide, 5 to B 0 5 to 8;

TiO 12 to 22 and A5203, 5 to 6.

4. A glass composition consisting essentially of TiO P 0 A1 0 alkaline earth oxide, alkali metal oxide, B 0 and AS203, the glass having a refractive index (11 of about 1.6 to 1.75 and Abbe value (11) less than about 40 wherein the glass batch constituents consist essentially of:

aluminum metaphosphate, magnesium metaphosphate,

potassium metaphosphate, containing 1 to 10 weight percent, aluminum oxide, 1 to 10 percent magnesium oxide, 1 to 20 percent potassium oxide, and 30 to 60 percent phosphorus pentoxide;

3 to 18 percent boric oxide;

7 to 35 percent titanium dioxide; and

3 to 30 percent arsenous oxide.

5. A glass composition consisting essentially of TiO P 0 Al O alkaline earth oxide, alkali metal oxide, B 0 and AS203, the glass having a refractive index (11 of about 1.6 to 1.75 and Abbe value (1 less than about 40 wherein the glass batch constituents consist essentially of: about 19.0 weight percent Al(PO 31.8 percent Mg(PO 18.6 percent KPO 6.2 percent B 0 19.0 percent TiO 5.5 percent As O 6. The glass composition of claim 5 having refractive index of about 1.66 and Abbe value (v) of about 28.5.

7. A glass batch composition consisting essentially of:

1 to 10 weight percent A1 0 1 to 10 percent MgO,

1 to 20 percent K 0,

30 to 60 percent P 0 3 to 18 percent B 0 7 to 35 percent TiO and 3 to 30 percent AS203.

8. The glass batch composition of claim 7 consisting essentially of 2 to 7 percent A1 0 2 to 8 percent MgO,

4 to 15 percent K 0,

to 55 percent P 0 4 to 15 percent B 0 8.5 to 25 percent TiO and 4 to 7 percent As O 9. The glass batch composition of claim 7 consisting essentially of:

3 to 4 percent A1 0 5 to 7 percent MgO,

5 to 10 percent K 0,

to percent P 0 5 to 8 percent B 0 12 to 22 percent TiO and 5 to 6 percent AS203.

References Cited UNITED STATES PATENTS 2,999,819 9/1961 Blair 106-47 X 3,068,108 12/1962 Geffcken 10647 3,100,714 8/1963 Bromer et a1. 106-47 X 3,328,181 6/1967 Weidel 10647 FOREIGN PATENTS 1,003,926 3/ 1957 Germany.

JAMES E. POER, Primary Examiner W. R. SATTERFIELD, Assistant Examiner 

